Search Results

The ideal attributes of light weight, low cost and high power density have made the 2-stroke engine unrivalled in the scooter and moped market for many years. However, the challenges of meeting new emissions regulations, especially the latest Euro III emission test cycle have reduced the 2-stroke's dominance and it is now often considered to be too dirty and inefficient to have a future. As a result its product placement is on the decline. This paper introduces and discusses the latest application of a low-cost high-frequency injection system (Pulse Count Injection [ 1 , 2 ]) to both the fuel flow and lubrication oil flow of a 2-stroke scooter; allowing both fluids to be individually mapped and optimised for the complete engine operating range. This in turn enables the 2-stroke engine to pass the latest Euro III test whilst improving the fuel economy by a considerable margin, without changing the architecture of the engine.

The application of hybridization technology is now widely regarded as a significant step forward to reduce fuel consumption and hence CO₂ emissions for ground vehicles. Many programs and much research has been done on these technologies in the automotive market, however little work has been done in the very cost sensitive market sector of the small motorcycle. This paper introduces and discusses the application of a low-cost hybrid technology to small motorcycles and scooters, and reviews some of the initial trade-offs through the use of a new hybrid simulation model developed at Cranfield University. The study being presented assessed the existing Energy Storage Systems (ESS) in the market. This list was reduced, omitting options which posed a clear safety or cost risk, or solutions which would disproportionally increased the Gross Vehicle Weight (GVW). Also omitted were storage options which could not be production ready in the near term, 3 - 5 years.

As a result of environmental pressures and end-user demands many manufacturers are working on fuel injection systems for the small engines market [reference 1, 2, 3, 4, 5]. A common approach is to take an automotive or motorcycle system and work to reduce its cost and complexity. This paper will present an engine management system designed from the outset specifically for low cost small engines. The key topics covered in this paper are sensor selection & minimisation, practical application of electronic throttle & ignition, power consumption minimisation and discussion of the software control strategy. In conclusion, this paper shows that most components required for a small engine management system can be integrated into a throttle body requiring only 3 external components. It is also possible, with the addition of electronic throttle and ignition, to deliver significant user enhancements.

With increasing pressures to reduce engine emissions in the small engines market there is a need to precisely meter the fuel flow into the engine under all running conditions. Therefore this cost competitive market requires a well engineered injection system that combines good control of fuel metering at all speed / load conditions, and meets the markets competitive pricing requirements. It must also offer the potential to allow these engines to meet stringent future legislation, leading to the addition of closed loop control with 3 way catalysts. This paper presents an experimental investigation into the effect of wall wetting and fuel injection strategy on a small engine. The engine was fitted with a novel form of port fuel injection, Pulse Count Injection (PCI) [1.] This novel high frequency digital fuelling system allows rapid oscillation of the fuel quantity from one engine cycle to the next.

Small engines (<19kW) are used in many off-road applications, in both the domestic and industrial markets. The dominant driving force in these markets is cost; therefore the vast majority of these engines still use low cost carburettors to meter the fuel into the intake port. However all these engines are now facing increasingly strict emission targets and hence require new technologies to meet these new regulations, but any new technology must be extremely cost effective to be applicable. The conventional fuel injection solutions used for many years in the automotive market require complex systems including a fuel pump, pressure regulator, and fuel injector coupled to a sophisticated control module and a multitude of sensors. This type of solution is far too complex and expensive for the vast majority of engines in the small engines market, and would cost significantly more than the engine itself. A novel solution to this problem is high-frequency Pulse Count Injection (PCI).

Most small engine manufacturers are looking to introduce fuel control technology to reduce engine out emissions, however most available conventional fuel injectors consume high levels of power to achieve controlled injection and suitable atomisation of the fuel. Typical fuel injection pressures of 300kPa are required to achieve pulsed injection and up to 10MPa to achieve full atomisation. The addition of an extra air delivery system at pressures of 600kPa can also be employed to atomise the fuel. These methods require many 100's of Watt's of power making them unsuitable for the vast majority of small engine applications. This paper presents experimental data from a novel electrostatic atomiser designed specifically for application to small engines, with very low power requirements and excellent fuel atomisation.

The use of Direct Injection for spark ignition engines is increasing, with a noticeable trend towards smaller flow orifices as the requirement for improved atomisation increases and improved manufacturing capabilities allow micron sized holes to be mass produced. It is necessary therefore to develop test rigs and diagnostic techniques that will allow the collection of data from inside real sized nozzles in order to validate CFD models and allow optimized nozzle geometries to be rapidly designed and produced. This paper demonstrates real sized optical nozzles and diagnostic techniques that have allowed geometry evaluation and optimization in pressure swirl and plain orifice nozzles as small as 150μm.

This paper outlines a vision of future engine requirements and operating strategies to reduce fuel consumption and engine out emissions. It discusses in detail the valve operating strategies used to achieve throttleless spark ignition (SI) load control and two methods of controlled Auto Ignition (AI). Emission and fuel consumption speed load maps are shown and differences between SI and AI maps are discussed. Many fully variable valve-timing strategies are proposed and conclusions are reached that clearly indicate significant improvements in IC engine performance are still achievable.

Controlled auto ignition (CAI) is a form of combustion which uses an auto-ignited homogeneous air/fuel mixture but is controlled (or moderated) by regulating the quantity of internal exhaust gas residuals. In this paper, using a fully variable valve train and a newly developed exhaust valve control strategy, we substituted EGR with hot nitrogen or hot air. We found that the internal exhaust gas residuals have both thermal and chemical effects on CAI combustion. To investigate the thermal effect, nitrogen was used as it is a chemically inert gas. Although its temperature was raised to that of the internal exhaust gas residuals during testing, CAI combustion could not be promoted without assistance from a spark in a form of hybrid CAI, thus indicating that exhaust gas residuals have a chemical effect as well.

Recently [SAE 2001-01-0251], we reported for the first time on using a fully variable valve train (FVVT) to facilitate controlled auto-ignition (CAI) in 4-stroke gasoline engines, with a 23% reduction in fuel consumption and a reduction of up to 95% in emission levels. In this paper we look at the industry trends towards increased control over combustion related processes occurring in modern engines, which signaled the direction towards the CAI work, and review a range of valve train technologies available to meet these trends. Previous key work conducted by industry and academic researchers is also reviewed to establish a minimum specification requirement for the new fully variable valve train systems. The paper then describes two electro-hydraulic valve actuation systems capable of meeting these specifications, the first a research grade system used on single cylinder engines and the second a new production viable system that is aimed at bringing FVVT's to high volume production.

Two methods have been achieved of facilitating controlled auto-ignition (CAI) combustion in a 4-stroke engine. This has been accomplished without the need to pre-heat intake air and was made possible through the use of the Active Valve Train (AVT) system. AVT was used to vary the amount of trapped exhaust gasses (otherwise known as exhaust residuals) inside the cylinder prior to the compression stroke. Both methods represent examples of internal exhaust gas recirculation (EGR). It was observed that the amount of internal EGR determined the combustion initiation point as a function of crank angle, thus demonstrating that both methods are controllable reproducible processes. Initial results (taken at 2000rpm and 3.5bar IMEP) show that this combustion significantly reduces NOx emissions to ultra-low levels compared to conventional spark ignition combustion. Data presented here represents the first published results of our internal EGR methodologies.

The purpose of the ELEVATE (European Low Emission V4 Automotive Two-stroke Engine) industrial research project is to develop a small, compact, light weight, high torque and highly efficient clean gasoline 2-stroke engine of 120 kW which could industrially replace the relatively big existing automotive spark ignition or diesel 4-stroke engine used in the top of the mid size or in the large size vehicles, including the minivan vehicles used for multi people and family transportation. This new gasoline direct injection engine concept is based on the combined implementation on a 4-stroke bottom end of several 2-stroke engine innovative technologies such as the IAPAC compressed air assisted direct fuel injection, the CAI (Controlled Auto-Ignition) combustion process, the D2SC (Dual Delivery Screw SuperCharger) for both low pressure engine scavenging and higher pressure IAPAC air assisted DI and the ETV (Exhaust charge Trapping Valve).