C.A.V. Unit for fluorescent Lamps Pr next autumn C.A.V., Ltd., should
Page 79
If you've noticed an error in this article please click here to report it so we can fix it.
have put into production a'converter unit to allow fluorescent tubes to be run from a 24v. D.C. supply. At present a prototype unit is undergoing tests under service conditions.
This was disclosed by Mr. H. P. Asthury during the question time which followed the reading of two papers at the C.A.V. southern area agents' conference in Eastbourne last week.
Commenting on this information, Mr. W. J. Evans, general manager, Reading Transport Department, stated that his organization's experimental use of fluorescent lighting on double-deck vehicles had met with approval from both the public and platform staff. A converter was on display in a static exhibition at the conference. It incorporates transistors and is compact.
Another fact revealed was that silicondiode rectification equipment for A.C. generators would be available shortly for commercial vehicles. (Joseph Lucas, Lid., have already announced an A.C. generator fitted with this type of rectfficalion for cars and light vans.)
Use of silicon in place of selenium or germanium permits a .saving in weight and space whilst giving greater efficiency. If produced in quantity, silicon rectifiers wo Id probably be cheaper than the other two types, Dr. A. E. W. Austen, chief engineer, C.A.V., Ltd., outlined the research undertaken by the concern into combustion and injection characteristics. He started with the premise that "we are obviously very close to the limits of what is the retically impossible as regards [fuel] co sumption, but there may be something to tome in maximum power and torque."
To obtain the greatest possible effiiericy, the complete fuel charge in the cylinder of an oil engine should be burnt instantaneously with the piston at top dead centre. However, this would produ c excessively high cylinder pressures. It as essential to smooth the rate of pressure rise and Control combustion to pr vide almost constant• acceptable pr4ssures.
lthough many of the problems of coiibustion could be resolved by calculatie , practical research was vital. C.A.V. hadeveloped or acquired, over a period of 'ears, ears, equipment for measuring cylinder pressures, fuel flow and injector .needle lift.
By using these devices it was possible to assess the relationship between fuel flow and cylinder pressure, which, for any given direct-injection engine, was approximately consistent irrespective of load, speed or timing.
Once the relationship had been agreed for any injection characteristic, it was possible to determine the cylinder pressures with any other form of fuel flow.
Noise had received much attention: Although " knock " was the main noise source of the engine, actual sound emission from the unit was greatly affected by its structure. Dr. Austen played recordings of two comparable 2-litre oil engines. One was much noisier than the other yet had a much quieter cylinder-pressure analysis. Thus the engine mass itself had amplified and propagated cylinder noise. whilst the structure of the other engine had tended to damp it.
Other recordings showed how a marked reduction in the noise level of some units could be made by . replacing resonant engine components by " dead " structures Examination of the combustion process had been aided by photographing the inside of a combustion chamber through a quartz window. A film was shown of tests on heater pings which indicated that the heater actually served as an ignition point in the chamber and did not, as commonly supposed, merely warm the air to the point of combustion.