In part 1, I – Keith Douglas, Performance Engineering Director – looked at how Bowman’s eTurbo Systems technology can not only help make the use of existing fuels more efficient and thus dramatically lower emissions, but how they can also enable the use of non-traditional and blended fuels by greatly enhancing engine adaptability. In part 2, I describe how eTurbo Systems technology can also allow the use of carbon-free fuels in ICEs (Internal Combustion Engines) and improve the performance and efficiency of fuel cells.
Engine companies are currently developing solutions to overcome the challenges of ensuring the homogeneous mixing of hydrogen and controlling its combustion in high-speed Spark-Ignited (SI) ICEs. With Miller cycle, and Lambda (λ, the ratio of the amount of oxygen present in a combustion chamber compared to the amount for “perfect” combustion) in the region of 2.5, ultra-low engine NOx emissions are being achieved. This means approximately 50% more air is required versus today’s diesel or NG (Natural Gas) equivalents. Throw into the mix turbine inlet temperatures below 500°C (less than with diesel or NG) and the turbocharging equation doesn’t quite balance; there is not enough exhaust energy available to meet high boost pressure demands. In other words, when it comes to high-speed SI hydrogen ICE’s, the turbo system is a limiting factor in achieving the power densities we are accustomed to with today’s fossil-fuelled versions. Bowman’s eCompressor and eTurbocharger technologies can help overcome these challenges in two ways:
- By electrically supplementing the available exhaust energy to directly meet the steady-state boost pressure requirements for high power density. This ability to electrically increase boost pressure can also be used to lighten the burden on the ICE’s turbocharger, enabling large turbine areas to be used and ensuring a positive scavenging pressure (delta pressure from the intake manifold to the exhaust manifold) is achieved. This guarantees a good engine pumping efficiency but, more critically for hydrogen combustion, minimises in-cylinder residual exhaust gas fraction thus increasing resistance to autoignition/end gas detonation (also known as ‘knock’).
- Bowman’s best-in-class power electronic (PE) torque response also allows a novel turbocharger matching approach to be taken. Millisecond regulation of the eTurbo System speed allows the ICE to be governed by the eTurbo System itself, negating the need for a throttle or bypass valve for steady-state control. All the margins traditionally designed into the ICE turbocharger match for steady-state governing control, high ambient temperatures, high altitudes, engine ageing, etc., no longer need to be accommodated. This allows the turbocharger work to be further decreased, bringing the turbocharger’s compressor ratio and turbine expansion ratio requirements down, and additionally the boost pressure requirement for the hydrogen ICE down.
As an example, let’s take a baseline high-speed 20bar BMEP (Brake Mean Effective Pressure), lean-burn, Miller cycle, NG ICE which has had the combustion system converted to run on 100% hydrogen. With a conventional single-stage turbocharger, the maximum output of the ICE would need to be derated (less power) by >30% to stay within turbocharger limits and enable combustion conditions favourable for hydrogen (positive scavenging pressure). Applying a single stage eTurbocharger, as described above, the full ICE derate can be recovered, achieving 20bar BMEP at 2.5λ, with the power needed for the electrical assistance from the eTurbocharger equivalent to approximately 5% of the ICE full load power. Also, with this approach, the ICE could be switched back to running 100% NG at 20bar BMEP and meet the new boost pressure requirements (~1.8λ), without changing the eTurbocharger hardware. In that scenario, there would be heat recovery opportunity from the eTurbocharger of approximately 5% (of the ICE full power rating), so additional power can be generated, improving on the baseline NG ICE efficiency. Huge possibilities therefore exist with eTurbo Systems to give flexibility to run ICEs continuously without derate on 100% hydrogen, or with extra power/lower fuel consumption on 100% NG, or with any blend in-between. With the uncertainties around the future of green hydrogen gas production from day to day or season to season, this will be a great enabler for ICE power systems in the coming years.
Furthermore, hydrogen ICE transients will be a huge challenge; even more air delivery will be needed to shift between loads versus today’s status quo, and even tighter λ control will be needed to keep the combustion under control. Applying eTurbo Systems will be necessary to achieve good transient performance and, using Bowman’s expertise, the cooling and sizing of the power electronics (PE) and shaft electric motor can be optimised so that high magnitude, short-term torque pulses can be applied to accelerate or decelerate the eTurbo System shaft within mere milliseconds. Challenging transient profiles can be achieved while delivering the air required, ensuring tight cycle-to-cycle combustion and emissions control throughout.
Switching focus to fuel cells, two types are gathering momentum in the field: PEMFCs (Proton Exchange Membrane), which are hydrogen-compatible, and SOFCs (Solid Oxide), which are hydrocarbon- and hydrogen-compatible. These each have very different exhaust energies available and thus different requirements for the turbo system.
Hydrogen PEM fuel cells exhibit much lower exhaust temperatures than SI hydrogen ICEs, with 80-90°C being typical. Similarly, but in much higher relative terms, torque needs to be continuously added to the eTurbo system shaft to deliver the air at the pressures required to achieve satisfactory power density. eCompressors and eTurbochargers can be used, with approximately 20% and 13% (parasitic power consumption) of the total fuel cell power output required to drive the eTurbo systems respectively. Taking the magnitude of these parasitic losses at the fuel cell system level into account, and considering the near-term cost of hydrogen, eTurbo Systems efficiency and Bowman’s knowhow in matching and optimising the system to the load profile and duty cycle is critical to achieving competitive fuel cell lifecycle costs.
Hydrogen SOFCs tend to operate at temperatures more akin to today’s ICEs, with exhaust temperatures typically between 650°C and 950°C. SOFCs are thus ideal candidates for turbomachinery layouts that utilise this high-grade exhaust energy, with applications today commonly targeting CHP (Combined Heat and Power) applications. The energy available within the exhaust is more than adequate to use a turbocharger to deliver the air requirements for the SOFC, and by additionally applying eTurbocharger technology, opportunities exist to continuously generate electrical torque from the shaft. Depending on the pressure levels the SOFC can be designed for and achieve, it is feasible that electrical powers in excess of 20% (additional power) of the SOFC power can be harvested from the eTurbocharger shaft.
Whether improving the efficiency of today’s ICEs, or enabling the transition to future carbon-neutral ICE and fuel cell power systems, the ability to continuously or transiently add or harvest torque from the motor / generator shaft of a turbo system makes eTurbo Systems technology a crucial path to success.
In part 1, I – Keith Douglas, Performance Engineering Director – looked at how Bowman’s eTurbo Systems technology can not only help make the use of existing fuels more efficient and thus dramatically lower emissions, but how they can also enable the use of non-traditional and blended fuels by greatly enhancing engine adaptability. In part 2, I describe how eTurbo Systems technology can also allow the use of carbon-free fuels in ICEs (Internal Combustion Engines) and improve the performance and efficiency of fuel cells.
Engine companies are currently developing solutions to overcome the challenges of ensuring the homogeneous mixing of hydrogen and controlling its combustion in high-speed Spark-Ignited (SI) ICEs. With Miller cycle, and Lambda (λ, the ratio of the amount of oxygen present in a combustion chamber compared to the amount for “perfect” combustion) in the region of 2.5, ultra-low engine NOx emissions are being achieved. This means approximately 50% more air is required versus today’s diesel or NG (Natural Gas) equivalents. Throw into the mix turbine inlet temperatures below 500°C (less than with diesel or NG) and the turbocharging equation doesn’t quite balance; there is not enough exhaust energy available to meet high boost pressure demands. In other words, when it comes to high-speed SI hydrogen ICE’s, the turbo system is a limiting factor in achieving the power densities we are accustomed to with today’s fossil-fuelled versions. Bowman’s eCompressor and eTurbocharger technologies can help overcome these challenges in two ways:
- By electrically supplementing the available exhaust energy to directly meet the steady-state boost pressure requirements for high power density. This ability to electrically increase boost pressure can also be used to lighten the burden on the ICE’s turbocharger, enabling large turbine areas to be used and ensuring a positive scavenging pressure (delta pressure from the intake manifold to the exhaust manifold) is achieved. This guarantees a good engine pumping efficiency but, more critically for hydrogen combustion, minimises in-cylinder residual exhaust gas fraction thus increasing resistance to autoignition/end gas detonation (also known as ‘knock’).
- Bowman’s best-in-class power electronic (PE) torque response also allows a novel turbocharger matching approach to be taken. Millisecond regulation of the eTurbo System speed allows the ICE to be governed by the eTurbo System itself, negating the need for a throttle or bypass valve for steady-state control. All the margins traditionally designed into the ICE turbocharger match for steady-state governing control, high ambient temperatures, high altitudes, engine ageing, etc., no longer need to be accommodated. This allows the turbocharger work to be further decreased, bringing the turbocharger’s compressor ratio and turbine expansion ratio requirements down, and additionally the boost pressure requirement for the hydrogen ICE down.
As an example, let’s take a baseline high-speed 20bar BMEP (Brake Mean Effective Pressure), lean-burn, Miller cycle, NG ICE which has had the combustion system converted to run on 100% hydrogen. With a conventional single-stage turbocharger, the maximum output of the ICE would need to be derated (less power) by >30% to stay within turbocharger limits and enable combustion conditions favourable for hydrogen (positive scavenging pressure). Applying a single stage eTurbocharger, as described above, the full ICE derate can be recovered, achieving 20bar BMEP at 2.5λ, with the power needed for the electrical assistance from the eTurbocharger equivalent to approximately 5% of the ICE full load power. Also, with this approach, the ICE could be switched back to running 100% NG at 20bar BMEP and meet the new boost pressure requirements (~1.8λ), without changing the eTurbocharger hardware. In that scenario, there would be heat recovery opportunity from the eTurbocharger of approximately 5% (of the ICE full power rating), so additional power can be generated, improving on the baseline NG ICE efficiency. Huge possibilities therefore exist with eTurbo Systems to give flexibility to run ICEs continuously without derate on 100% hydrogen, or with extra power/lower fuel consumption on 100% NG, or with any blend in-between. With the uncertainties around the future of green hydrogen gas production from day to day or season to season, this will be a great enabler for ICE power systems in the coming years.
Furthermore, hydrogen ICE transients will be a huge challenge; even more air delivery will be needed to shift between loads versus today’s status quo, and even tighter λ control will be needed to keep the combustion under control. Applying eTurbo Systems will be necessary to achieve good transient performance and, using Bowman’s expertise, the cooling and sizing of the power electronics (PE) and shaft electric motor can be optimised so that high magnitude, short-term torque pulses can be applied to accelerate or decelerate the eTurbo System shaft within mere milliseconds. Challenging transient profiles can be achieved while delivering the air required, ensuring tight cycle-to-cycle combustion and emissions control throughout.
Switching focus to fuel cells, two types are gathering momentum in the field: PEMFCs (Proton Exchange Membrane), which are hydrogen-compatible, and SOFCs (Solid Oxide), which are hydrocarbon- and hydrogen-compatible. These each have very different exhaust energies available and thus different requirements for the turbo system.
Hydrogen PEM fuel cells exhibit much lower exhaust temperatures than SI hydrogen ICEs, with 80-90°C being typical. Similarly, but in much higher relative terms, torque needs to be continuously added to the eTurbo system shaft to deliver the air at the pressures required to achieve satisfactory power density. eCompressors and eTurbochargers can be used, with approximately 20% and 13% (parasitic power consumption) of the total fuel cell power output required to drive the eTurbo systems respectively. Taking the magnitude of these parasitic losses at the fuel cell system level into account, and considering the near-term cost of hydrogen, eTurbo Systems efficiency and Bowman’s knowhow in matching and optimising the system to the load profile and duty cycle is critical to achieving competitive fuel cell lifecycle costs.
Hydrogen SOFCs tend to operate at temperatures more akin to today’s ICEs, with exhaust temperatures typically between 650°C and 950°C. SOFCs are thus ideal candidates for turbomachinery layouts that utilise this high-grade exhaust energy, with applications today commonly targeting CHP (Combined Heat and Power) applications. The energy available within the exhaust is more than adequate to use a turbocharger to deliver the air requirements for the SOFC, and by additionally applying eTurbocharger technology, opportunities exist to continuously generate electrical torque from the shaft. Depending on the pressure levels the SOFC can be designed for and achieve, it is feasible that electrical powers in excess of 20% (additional power) of the SOFC power can be harvested from the eTurbocharger shaft.
Whether improving the efficiency of today’s ICEs, or enabling the transition to future carbon-neutral ICE and fuel cell power systems, the ability to continuously or transiently add or harvest torque from the motor / generator shaft of a turbo system makes eTurbo Systems technology a crucial path to success.
In part 1, I – Keith Douglas, Performance Engineering Director – looked at how Bowman’s eTurbo Systems technology can not only help make the use of existing fuels more efficient and thus dramatically lower emissions, but how they can also enable the use of non-traditional and blended fuels by greatly enhancing engine adaptability. In part 2, I describe how eTurbo Systems technology can also allow the use of carbon-free fuels in ICEs (Internal Combustion Engines) and improve the performance and efficiency of fuel cells.
Engine companies are currently developing solutions to overcome the challenges of ensuring the homogeneous mixing of hydrogen and controlling its combustion in high-speed Spark-Ignited (SI) ICEs. With Miller cycle, and Lambda (λ, the ratio of the amount of oxygen present in a combustion chamber compared to the amount for “perfect” combustion) in the region of 2.5, ultra-low engine NOx emissions are being achieved. This means approximately 50% more air is required versus today’s diesel or NG (Natural Gas) equivalents. Throw into the mix turbine inlet temperatures below 500°C (less than with diesel or NG) and the turbocharging equation doesn’t quite balance; there is not enough exhaust energy available to meet high boost pressure demands. In other words, when it comes to high-speed SI hydrogen ICE’s, the turbo system is a limiting factor in achieving the power densities we are accustomed to with today’s fossil-fuelled versions. Bowman’s eCompressor and eTurbocharger technologies can help overcome these challenges in two ways:
- By electrically supplementing the available exhaust energy to directly meet the steady-state boost pressure requirements for high power density. This ability to electrically increase boost pressure can also be used to lighten the burden on the ICE’s turbocharger, enabling large turbine areas to be used and ensuring a positive scavenging pressure (delta pressure from the intake manifold to the exhaust manifold) is achieved. This guarantees a good engine pumping efficiency but, more critically for hydrogen combustion, minimises in-cylinder residual exhaust gas fraction thus increasing resistance to autoignition/end gas detonation (also known as ‘knock’).
- Bowman’s best-in-class power electronic (PE) torque response also allows a novel turbocharger matching approach to be taken. Millisecond regulation of the eTurbo System speed allows the ICE to be governed by the eTurbo System itself, negating the need for a throttle or bypass valve for steady-state control. All the margins traditionally designed into the ICE turbocharger match for steady-state governing control, high ambient temperatures, high altitudes, engine ageing, etc., no longer need to be accommodated. This allows the turbocharger work to be further decreased, bringing the turbocharger’s compressor ratio and turbine expansion ratio requirements down, and additionally the boost pressure requirement for the hydrogen ICE down.
As an example, let’s take a baseline high-speed 20bar BMEP (Brake Mean Effective Pressure), lean-burn, Miller cycle, NG ICE which has had the combustion system converted to run on 100% hydrogen. With a conventional single-stage turbocharger, the maximum output of the ICE would need to be derated (less power) by >30% to stay within turbocharger limits and enable combustion conditions favourable for hydrogen (positive scavenging pressure). Applying a single stage eTurbocharger, as described above, the full ICE derate can be recovered, achieving 20bar BMEP at 2.5λ, with the power needed for the electrical assistance from the eTurbocharger equivalent to approximately 5% of the ICE full load power. Also, with this approach, the ICE could be switched back to running 100% NG at 20bar BMEP and meet the new boost pressure requirements (~1.8λ), without changing the eTurbocharger hardware. In that scenario, there would be heat recovery opportunity from the eTurbocharger of approximately 5% (of the ICE full power rating), so additional power can be generated, improving on the baseline NG ICE efficiency. Huge possibilities therefore exist with eTurbo Systems to give flexibility to run ICEs continuously without derate on 100% hydrogen, or with extra power/lower fuel consumption on 100% NG, or with any blend in-between. With the uncertainties around the future of green hydrogen gas production from day to day or season to season, this will be a great enabler for ICE power systems in the coming years.
Furthermore, hydrogen ICE transients will be a huge challenge; even more air delivery will be needed to shift between loads versus today’s status quo, and even tighter λ control will be needed to keep the combustion under control. Applying eTurbo Systems will be necessary to achieve good transient performance and, using Bowman’s expertise, the cooling and sizing of the power electronics (PE) and shaft electric motor can be optimised so that high magnitude, short-term torque pulses can be applied to accelerate or decelerate the eTurbo System shaft within mere milliseconds. Challenging transient profiles can be achieved while delivering the air required, ensuring tight cycle-to-cycle combustion and emissions control throughout.
Switching focus to fuel cells, two types are gathering momentum in the field: PEMFCs (Proton Exchange Membrane), which are hydrogen-compatible, and SOFCs (Solid Oxide), which are hydrocarbon- and hydrogen-compatible. These each have very different exhaust energies available and thus different requirements for the turbo system.
Hydrogen PEM fuel cells exhibit much lower exhaust temperatures than SI hydrogen ICEs, with 80-90°C being typical. Similarly, but in much higher relative terms, torque needs to be continuously added to the eTurbo system shaft to deliver the air at the pressures required to achieve satisfactory power density. eCompressors and eTurbochargers can be used, with approximately 20% and 13% (parasitic power consumption) of the total fuel cell power output required to drive the eTurbo systems respectively. Taking the magnitude of these parasitic losses at the fuel cell system level into account, and considering the near-term cost of hydrogen, eTurbo Systems efficiency and Bowman’s knowhow in matching and optimising the system to the load profile and duty cycle is critical to achieving competitive fuel cell lifecycle costs.
Hydrogen SOFCs tend to operate at temperatures more akin to today’s ICEs, with exhaust temperatures typically between 650°C and 950°C. SOFCs are thus ideal candidates for turbomachinery layouts that utilise this high-grade exhaust energy, with applications today commonly targeting CHP (Combined Heat and Power) applications. The energy available within the exhaust is more than adequate to use a turbocharger to deliver the air requirements for the SOFC, and by additionally applying eTurbocharger technology, opportunities exist to continuously generate electrical torque from the shaft. Depending on the pressure levels the SOFC can be designed for and achieve, it is feasible that electrical powers in excess of 20% (additional power) of the SOFC power can be harvested from the eTurbocharger shaft.
Whether improving the efficiency of today’s ICEs, or enabling the transition to future carbon-neutral ICE and fuel cell power systems, the ability to continuously or transiently add or harvest torque from the motor / generator shaft of a turbo system makes eTurbo Systems technology a crucial path to success.