Analysis of a novel mild air hybrid engine technology, RegenEBD, for buses and commercial vehicles

Abstract

In this paper, a novel cost-effective mild air hybrid engine concept for buses and commercial vehicles, RegenEBD, is presented. This air hybrid technology is designed to convert kinetic energy into pneumatic energy of the compressed air stored in the air tank normally installed on such vehicles. The compressed air can then be used to drive an air starter to achieve regenerative stop–start operations for buses and delivery vehicles with frequent stop–start operations. For other commercial vehicles, it can provide service air required for braking and pneumatic operations and reduce the usage of the engine driven compressor. Furthermore, the availability of the free compressed air can be used to provide instant boost to a turbocharged engine at start-up and during acceleration for better performance and improved fuel economy. A six-cylinder diesel engine has been modelled to operate as a mild air hybrid engine and analysed using an engine simulation programme. In addition, a newly developed air hybrid vehicle driving cycle simulation programme has been applied to analyse the charging and discharging processes during a typical London Bus route and a German Braunschweig city cycle. The analysis shows that with the RegenEBD, almost all the idling periods can be eliminated through regenerative stop–start operations, resulting in a fuel saving of 6.5–7.2%.

Experimental studies of the air hybrid engine charging operation

“…This provides the basis of the engine response map of the compressor mode operation comprising engine braking torque values as a function of throttle positions, which has been used for the vehicle driving cycle analysis. 10,11…”

“…Therefore, it has confirmed that the use of an intake throttle can be an effective means to controlling the engine braking torque in the air hybrid engine operations. This provides the basis of the engine response map of the compressor mode operation comprising engine braking torque values as a function of throttle positions, which has been used for the vehicle driving cycle analysis [10,11]. Table 4 shows an engine response map which summarises the tank pressure and the intake throttle valve opening as functions of the flow rate (g/cycle) of air mass charged for the engine speed range between 1000 and 2000 rpm.…”

“…This provides the basis of the engine response map of the compressor mode operation comprising engine braking torque values as a function of throttle positions, which has been used for the vehicle driving cycle analysis. 10,11 Table 4 shows an engine response map which summarises the tank pressure and the intake throttle valve opening as functions of the flow rate (g/cycle) of air mass charged for the engine speed range between 1000 and 2000 r/min. It shows the engine braking imep rather than engine braking torque for compressor mode because of the larger flywheel and higher frictional losses than the production engine.…”

Modified intake and exhaust system for piston-type compressed air engines

“…Thus, Andersson et al focused on using pressurized air instead of atmospheric air for cylinder charging [4]. Lee et al proposed a hybrid pneumatic power train in which two shutoff valves connected to a convenient access hole in the engine cylinder enable the cylinder to operate as a regenerative compressor and expander when required [5]. Tai et al utilized four fully-flexible camless valves (two intakes and two exhausts) for each cylinder.…”

Study of a hybrid pneumatic-combustion engine under steady-state and transient conditions for transport application

“…The simulation showed that the pneumatic hybridisation could recover about 10% of total energy under different conditions. Lee et al 23–25 studied a cost-effective mild hybrid pneumatic engine concept for buses and commercial vehicles. The simulation showed that the fuel mass consumed during the New European Driving Cycle (NEDC) was 677 g for a standard vehicle and 631.2 g for a hybrid pneumatic vehicle, indicating a fuel saving effect of 6.8%.…”