BIOGRAPHY OFATYPICAL ENGINE
This concluding section of the chapter is presented to show that all
specialties have a long way to go before we can truly say that engines can
be accurately designed. A lot of development work needs to be done in
order to produce a successful engine. Most of it has to be performed by
"greasy-fingered" engineers, who are often forced to work with trial-anderror
methods. They need all the useful help they can get from the various
specialties for reducing weight, improving fuel consumption, and increasing
both reliability and component life.
With respect to the biography, observe first that research is continually
being directed toward improving the capabilities of aircraft and engines.
General analyses of these results are periodically made to examine the
feasibility of improving existing airplanes, of making an airplane that will
either perform a useful service more economically, or of providing one that
was hitherto unavailable.
When the feasibility of an improved engine/airframe system is determined,
an analysis similar to that presented in Chapter 3 is initiated.
Engines and airplanes having the proposed advanced concepts are simulated
on large digital computers. Estimates are made of the properties and
behavior of every significant part of the engine and aircraft. Vital features
of the synthesized airplane are calculated along its proposed flight paths.
Numerous modifications of the synthesized engines and aircraft are examined
until the calculated optimum reliable airframe/engine combination for
the proposed mission is found.
The results are then reviewed to determine the worthiness of the airplane.
This review includes an estimate of the cost of designing and developing the
engine and airplane, the cost of manufacturing the desired number, and the
cost of operating and maintaining them over their expected life. These
economic evaluations (which are often identified by the words "cost of
ownership," "life-cycle-costs," or "return on investment") are repeated
throughout the life of the enterprise.
If a decision is made to proceed with the design and development of an
engine, the initial specifications are provided by the preceding studies. Tests
are begun on the various components to evaluate their effectiveness: i.e.,
how does the performance compare to that expected? Several design
modifications are frequently required to realize the initial expectations.
After the components are functioning reasonably well, they are assembled
into an engine to evaluate the overall performance and reliability.
Parts of new engines usually operate in more hostile environments than any
of their predecessors and unanticipated interactions among the parts (both
aerothermodynamic and mechanical) are occasionally encountered. Many
events can and do happen. Some problems can be rectified by minor
changes in the engine design. Others may require major redesigns that need
to be re-evaluated on component rigs. In some instances, added required
costs of time and money can put the project in jeopardy.
When the engine performs its functions on a test stand with sufficient
reliability, it is ready for flight tests. New interactions between the airframe
and the engine introduce additional problems. This is particularly true
when there is no previous experience with the maneuvers and flight regimes
demanded of the airplane. Expedited rebirth and development of critical
engine components have been necessary even at this late phase of development.
Dedicated and competent engineering teamwork usually solves the
problems, finally producing an airplane that meets its specifications.
After an engine has been certified by a government bureau, it enters its
intended service. When many hours of flight have elapsed, new major
problems have suddenly appeared. Although most of these are mechanical
(related to fatigue), they probably represent a poor tradeoff, initially made
with incomplete data, between aerodynamics and stress. New evaluations
and new designs have to be made and developed in a hurry to solve the
problems. Again, it is the teamwork of many talents that overcome the
difficulties.
This concluding section of the chapter is presented to show that all
specialties have a long way to go before we can truly say that engines can
be accurately designed. A lot of development work needs to be done in
order to produce a successful engine. Most of it has to be performed by
"greasy-fingered" engineers, who are often forced to work with trial-anderror
methods. They need all the useful help they can get from the various
specialties for reducing weight, improving fuel consumption, and increasing
both reliability and component life.
With respect to the biography, observe first that research is continually
being directed toward improving the capabilities of aircraft and engines.
General analyses of these results are periodically made to examine the
feasibility of improving existing airplanes, of making an airplane that will
either perform a useful service more economically, or of providing one that
was hitherto unavailable.
When the feasibility of an improved engine/airframe system is determined,
an analysis similar to that presented in Chapter 3 is initiated.
Engines and airplanes having the proposed advanced concepts are simulated
on large digital computers. Estimates are made of the properties and
behavior of every significant part of the engine and aircraft. Vital features
of the synthesized airplane are calculated along its proposed flight paths.
Numerous modifications of the synthesized engines and aircraft are examined
until the calculated optimum reliable airframe/engine combination for
the proposed mission is found.
The results are then reviewed to determine the worthiness of the airplane.
This review includes an estimate of the cost of designing and developing the
engine and airplane, the cost of manufacturing the desired number, and the
cost of operating and maintaining them over their expected life. These
economic evaluations (which are often identified by the words "cost of
ownership," "life-cycle-costs," or "return on investment") are repeated
throughout the life of the enterprise.
If a decision is made to proceed with the design and development of an
engine, the initial specifications are provided by the preceding studies. Tests
are begun on the various components to evaluate their effectiveness: i.e.,
how does the performance compare to that expected? Several design
modifications are frequently required to realize the initial expectations.
After the components are functioning reasonably well, they are assembled
into an engine to evaluate the overall performance and reliability.
Parts of new engines usually operate in more hostile environments than any
of their predecessors and unanticipated interactions among the parts (both
aerothermodynamic and mechanical) are occasionally encountered. Many
events can and do happen. Some problems can be rectified by minor
changes in the engine design. Others may require major redesigns that need
to be re-evaluated on component rigs. In some instances, added required
costs of time and money can put the project in jeopardy.
When the engine performs its functions on a test stand with sufficient
reliability, it is ready for flight tests. New interactions between the airframe
and the engine introduce additional problems. This is particularly true
when there is no previous experience with the maneuvers and flight regimes
demanded of the airplane. Expedited rebirth and development of critical
engine components have been necessary even at this late phase of development.
Dedicated and competent engineering teamwork usually solves the
problems, finally producing an airplane that meets its specifications.
After an engine has been certified by a government bureau, it enters its
intended service. When many hours of flight have elapsed, new major
problems have suddenly appeared. Although most of these are mechanical
(related to fatigue), they probably represent a poor tradeoff, initially made
with incomplete data, between aerodynamics and stress. New evaluations
and new designs have to be made and developed in a hurry to solve the
problems. Again, it is the teamwork of many talents that overcome the
difficulties.
No comments:
Post a Comment