Tailored Centrifugal Turbomachinery for Electric Fuel Cell Turbocharger

Hydrogen fuel cell technology is identified as one option for allowing efficient vehicular propulsion with the least environmental impact on the path to a carbon-free society. Since more than 20 years, IHI is providing charging systems for stationary fuel cell applications and since 2004 for mobile fuel cell applications. The power density of fuel cells substantially increases if the system is pressurized. However, contaminants from fuel cell system components like structural materials, lubricants, adhesives, sealants, and hoses have been shown to affect the performance and durability of fuel cells. Therefore, the charging system that increases the pressure and the power density of the stacks inevitably needs to be oil-free. For this reason, gas bearings are applied to support the rotor of a fuel cell turbocharger. It furthermore comprises a turbine, a compressor, and, on the same shaft, an electric motor. The turbine utilizes the exhaust energy of the stack to support the compressor and hence lower the required electric power of the air supply system. The presented paper provides an overview of the fuel cell turbocharger technology. Detailed performance investigations show that a single-stage compressor with turbine is more efficient compared to a two-stage compressor system with intercooler. The turbine can provide more than 30% of the required compressor power. Hence, it substantially increases the system efficiency. It is also shown that a fixed geometry turbine design is appropriate for most applications. The compressor is of a low specific speed type with a vaneless diffuser. It is optimized for operating conditions of fuel cell systems, which typically require pressure ratios in the range of 3.0.

Numerical Simulation of Flow across a Radial Turbine for Prediction of Shaft Power for Driving Automobile Air Conditioners

The exhaust gas spouting from the exhaust manifold into the radial inflow turbine coupled to an exhaust pipe of a 2.5L petrol engine has been computationally simulated in order to ascertain the extent of exhaust energy recoverability for driving the vehicle auxiliaries, using Autodesk CFD. In order to determine the amount of power available at the turbine shaft at varying engine speeds, properties of the flow and fluid spouting into the turbine from the engine and out of the turbine from the volute outlet were examined by applying the SST k-? turbulence model and advanced Petrov-Galerkin's advection scheme. For the test engine used with the operating range of 2000-6000rpm, at engine speeds up to 3000rpm, the available power was about 0.3kW. At 4000rpm, about 2.8kW of power is available at the turbine shaft, increasing to 7.7kW at 5000rpm and 43.6kW at 6000rpm. Curve-fitting shows that at 5500rpm, as much as 15kW reversible power can be extracted from a shaft coupled to the turbocharger turbine. With an electrically-assisted turbine component of the turbocharger used, the compressor of vapour compression refrigeration system of the vehicle will be efficiently driven at all engine speeds while exhaust energy recovery is achieved.

Experimental Study of a New Pneumatic Actuating System Using Exhaust Recycling

Pneumatic actuating systems are an important power system in industrial applications. Due to exhaust loss, however, pneumatic actuating systems have suffered from a low utilization of compressed air. To recycle the exhaust energy, a novel pneumatic circuit was proposed to realize energy savings through recycling exhaust energy. The circuit consisted of three two-position three-way switch valves, which were used to control the exhaust flows into a gas tank or the ambient environment. This paper introduced the energy recovery configuration and working principles and built a mathematical model of its working process. Then, the mathematical model was verified by experiments. Finally, through experiments in which the air supply pressure, the critical pressure and the volume of the gas tank were regulated, the energy recovery characteristics of the pneumatic actuating system were obtained. Using the new circuit, the experimental results showed that the energy recovery efficiency exceeded 23%. When the air supply pressure was set to 5 bar, 6 bar, and 7 bar, the time required for pneumatic actuation to complete the three working cycles were 5.2 s, 5.3 s, and 5.9 s, respectively. When the critical pressure was set to 0 bar, 0.5 bar, 1 bar, and 1.5 bar, the times for pneumatic actuation to complete the three working cycles were 4.9 s, 5.1 s, 5.2 s, and 5.3 s, respectively. When the volume of the gas tank was set to 2 L, 3 L, 4 L, and 5 L, the number of working cycles was 3, 4, 5, and 6, respectively. This paper provides a new method of cylinder exhaust recycling and lays a good foundation for pneumatic energy savings.

Numerical and experimental investigation of exhaust manifold configurations of turbo-charged diesel engines

The exhaust energy recovery is significant for engine fuel efficiency. However, the exhaust gas interference and the loss of flow affect the utilization of exhaust energy of multi cylinder turbocharged diesel engine seriously. In this paper, through Particle Image Velocimetry experiment and computational fluid dynamics simulation of exhaust T-junction flow field, the characteristics of junction local flow field and the law of energy loss are obtained. Based on the one dimensional simulation of engine working process, the exhaust available energy analysis is carried out, and the transmission of available energy of exhaust valve and various pipe systems under typical operating conditions is obtained. On this basis, five exhaust systems are designed, and the steady-state and transient performances are compared by bench tests. The results show that the shrinkage rate and the intersection angle of T-junction are the key factors affecting exhaust energy transmission and exhaust gas interference suppression. Reducing the branch pipe shrinkage rate leads to an increase in branch pipe flow loss, but it will also reduce the main pipe flow loss and exhaust gas interference. Reducing the angle between the main pipe and branch pipe is beneficial to the exhaust flow and exhaust energy recovery. The pulse converter exhaust system has a high exhaust available energy transmission rate; the Modular Pulse Converter system has superior fuel efficiency and transient response performance from the perspective of the entire engine operation range. The 90% response time difference between the five studied exhaust systems is about 0.41 s.

Available Energy in Cars’ Exhaust System for IoT Remote Exhaust Gas Sensor and Piezoelectric Harvesting

The exhaust system of the light-duty diesel engine has been evaluated as a potential environment for a mechanical energy recovery system for powering an IoT (Internet of Things) remote sensor. Temperature, pressure, gas speed, mass flow rate have been measured in order to characterize the exhaust gas. At any engine point explored, thermal energy is by far the most dominant portion of the exhaust energy, followed by the pressure energy and lastly kinetic energy is the smallest fraction of the exhaust energy. A piezoelectric flexible device has been tested as a possible candidate as an energy harvester converting the kinetic energy of the exhaust gas flow, with a promising amount of electrical energy generated in the order of microjoules for an urban or extra-urban circuit.